This is kinda my area and I have access to the actual study, so I'll try to deal with a couple specific things that have been noted and then go off on my general complaints.

Originally Posted by ermghoti

That's the first thing I thought. Even with before/after tests, IQ is so murky, I don't know how you could claim conclusive results.

For example, IQ compares one to one's peers. Fine, this keeps youngsters from being categorized as deficient. Well, if your development plateaus early, you fall behind your peers, you get into fights because you're not socializing properly, and your IQ tests lower.

They're going to have to demonstrate physical evidence of brain injury to prove anything, IMO.

It's not so much that IQ drops. IQ tests are renormed every so often to keep the mean at 100 and (against all personal observations) IQ has been trudging upwards with every successive generation, so older people perform under par on the newer tests. So it doesn't keep the youngsters from looking deficient. It ends up making us older folks look deficient if we take the newer tests.
It's called the Flynn Effect, and wikipedia has a pretty decent write up on it. http://en.wikipedia.org/wiki/Flynn_effect

They don't show any evidence of brain injury, either.

Originally Posted by Omega Supreme

I'd like to go on record folks that "if" you actually took a real IQ test it would take between 3-5 hours to complete. It consist of several different areas of exams and takes a few days to calculate the results. Anything else and you took a novelty test. In order for these facts to hold true. You would have to do a proper IQ test on a subject, have that subject get hit in the head a few times over a few years and recalculate that IQ test weighing in all factors that could corrupt the outcome.

So yeah.

There's some truth to that. What they took was a short version of the Peabody Picture Vocabulary Test- Revised and they did take it twice, at least. I don't know how this short version stacks up against the long version for this specific test: some of the abbreviated tests are actually pretty close to the long version while others just... aren't.

OK... on to my complaints. First of all, it's a longitudinal study and Omega is right: this isn't an experiment so they can't really make a causal claim, but even the authors of the paper do. They're criminologists, it seems, and not psychologists and frankly I don't know what they're taught is appropriate methodology for making claims of causation from a correlation, but everyone around here knows the chant so I won't dwell on that too much more than to say that there's at least two possible alternative interpretations of the data: The first is stupid people get into more fights, thus increasing their chances of injury. The second is that stupid people are more likely to be "seriously injured" in fights. I'm leaning toward the former.

My second problem with this study is methodological and related to the causal claims... I can't tell for certain from what's presented in the study, but it looks like what they did was take the different "serious injury" groups from the 3rd data collection and compare them to the average from the first data collection, which if there are initial differences in IQ this would conceal them. The better way to do it if they want stronger causal evidence would be subdivide all the data at the beginning by injury group and then compare the changes within groups and then compare to the averages. It would have been easy to do and would have taken care of this question from the start, but I don't see it addressed. This makes me suspicious.

Third, they never define what a "serious injury" is and the data is self-report and even if they did the average IQ difference between one "serious" injury group and the next is extremely small: a 0.2 drop in IQ per serious injury in one year for females and less than a .1 drop for males. Surely physiological differences between males and females account for this, right? Wrong. Social pressures for females not to get into physical altercations are much higher than for males.
Note: OK, I see what they did. They're claiming a 1.62 loss per fight in a year for males and a 3.02 point loss per fight for females. I was looking at data presented at the end on a graph that's in standard deviations from the mean. Fuckers need to learn to label their god-damn y-axis.

Fourth problem. What did they control for? Age, socioeconomic status, race and gender. That's nice of them and all, but I want information on things like playing other contact sports, drug use and skipping school, for example.

So as far as I can tell this study is poorly designed, poorly executed and makes claims that it cannot back up.

If getting punched in the head = lower IQ...it stands to reason that people who are better able to maintain their intelligence do not train in arts that include regular punches to the head.

We know that 99.5% of Wing Chun schools basically have no contact, and thus, are likely to have less people whose IQ are being negatively affected by being punched in the head.

However, we also know, that a seemingly large majority of people who train Wing Chun clearly have some type of low-IQ-related disorder, as they have chosen to train a martial art that has, to an incredible extent, removed any semblance of being functionally martial.

So...how is it, that so many people who are taking such good care of their brains, can be so stupid?

If getting punched in the head = lower IQ...it stands to reason that people who are better able to maintain their intelligence do not train in arts that include regular punches to the head.

We know that 99.5% of Wing Chun schools basically have no contact, and thus, are likely to have less people whose IQ are being negatively affected by being punched in the head.

However, we also know, that a seemingly large majority of people who train Wing Chun clearly have some type of low-IQ-related disorder, as they have chosen to train a martial art that has, to an incredible extent, removed any semblance of being functionally martial.

So...how is it, that so many people who are taking such good care of their brains, can be so stupid?

I give you this quandary Bullshido. Please feel free to discuss.

Knowing enough to not get punched in the head>getting punched in the head>pretending that FOOMFOOMFOOM keeps one from getting punched in the head.

As someone mentioned previously, the IQ test is such a murky measure of "intelligence" (whatever the hell that is) it's virtually useless. It's like looking at a big, strong, person and saying that they are the best athlete. At what?

"We often joke -- and we really wish it were a joke -- that you will only encounter two basic problems with your 'self-defense' training.
1) That it doesn't work
2) That it does work"
-Animal MacYoung